| 摘要 |
<p>A process of imaging a film containing a photochromic compound, which is a fulgide or fulgimide that can reversibly be converted by UV light from a relatively colourless form to a coloured form, includes the step of exposing the film to UV light in one or more selected areas to convert the photochromic compound at least partially to the coloured form in those areas, the photochromic compound in the remaining areas being in the relatively colourless form. The process is characterised in that the film so exposed is heated, either simultaneously with its exposure to UV light or subsequently, to a temperature, preferably in the range 50-180 °C, at which the coloured form of the photochromic compound is degraded to a relatively colourless permanently non-photochromic compound but the relatively colourless form of the photochromic compound is not degraded. The image formed can be used as an identifying mark, particulary as a security marking for goods, packages, documents or identification cards.</p> |
